The short answer
A Gleason score is two pattern numbers added together, and their order matters: 3+4=7 is less aggressive than 4+3=7. Grade Groups fold every combination into a 1-to-5 scale. Group 1 is often watched with active surveillance rather than treated. Grade is not the same as stage.
Gleason 3+4=7 and 4+3=7 add to the same number but differ: more pattern 4 means a more aggressive cancer.
Grade Groups sort every Gleason combination into five categories, with Group 1 covering a score of 6 or lower.
Grade Group 1 cancer with a low PSA is often eligible for active surveillance rather than immediate treatment.
Grade describes the cells in your biopsy sample, not the whole gland, and it is not the same as stage.
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The full explanation.
What a Gleason score measures
A Gleason score describes how abnormal prostate cancer cells look under a microscope. A pathologist studies the tissue from your biopsy. They grade the pattern of the cells, not just how many there are. This tells your care team how the cancer is likely to behave.
The scale runs from pattern 3 to pattern 5. Pattern 3 looks the most like normal prostate tissue. Pattern 4 looks more abnormal. Pattern 5 looks the most abnormal, with cells that have lost their normal structure almost completely.
How two numbers become one score
Prostate tumors are rarely made of just one pattern. So pathologists grade the two most common patterns they see. The primary pattern takes up the most space in the sample. The secondary pattern is the next most common.
These two numbers are added together. A tumor that is mostly pattern 3, with some pattern 4, is written as Gleason 3+4=7. A tumor that is mostly pattern 4, with some pattern 3, is written as Gleason 4+3=7. Both add up to 7. But they are not the same cancer. More pattern 4 means a more aggressive cancer, even though the total score matches. This is why your report lists both numbers, not just the sum.
Gleason scores usually range from 6 to 10. A score below 6 is rarely reported today, since the mildest pattern grades are no longer commonly used.
Grade Groups: a simpler five-point scale
Because two different combinations can both add up to 7, doctors created a second system called Grade Groups. It sorts every Gleason combination into five simpler categories, numbered 1 through 5.
Grade Group 1 covers a Gleason score of 6 or lower. This is the least aggressive category. Grade Group 2 covers Gleason 3+4=7, where pattern 3 dominates. Grade Group 3 covers Gleason 4+3=7, where pattern 4 dominates. Grade Group 4 covers a Gleason score of 8. Grade Group 5 covers a Gleason score of 9 or 10, the most aggressive category.
Higher Grade Groups are linked with cancer that is more likely to grow and spread quickly. Your report may show both the Gleason score and the Grade Group together. They describe the same finding in two different ways.
What this changes about your options
Grade Group is one of the main factors used to plan prostate cancer treatment. It is weighed alongside your PSA level and the stage of the cancer. Grade Group 1 cancer, especially if it is small and PSA is low, is often eligible for active surveillance. That means monitoring the cancer closely with PSA tests, exams, and repeat biopsies, instead of treating it right away. Many men with Grade Group 1 cancer never need surgery or radiation.
Higher Grade Groups usually point toward more immediate treatment, such as surgery or radiation, sometimes combined with hormone therapy. The exact recommendation still depends on your PSA, your imaging results, your age, and your overall health.
What it does not tell you
A Grade Group describes the cells seen in your biopsy sample, not the whole prostate. A biopsy only samples part of the gland. The true highest-grade area could occasionally be missed. Grade also does not equal stage. Stage describes the size of the tumor and whether it has spread beyond the prostate. A Grade Group 4 cancer still confined to the prostate is a different situation from the same grade found alongside spread to lymph nodes or bone.
What to ask your team
- What is my Gleason score, written as two numbers, and what is my Grade Group?
- Is active surveillance an option for me, or does my grade point toward treatment now?
- How do my PSA level and imaging results fit with this grade?
- Could a repeat biopsy or more imaging change this picture?
Why a second pathologist sometimes reviews the slides
Gleason grading involves real judgment, and pattern 3 versus pattern 4 can be a close call in some samples. Because active surveillance decisions often hinge on this exact distinction, many centers routinely have a second, specialized pathologist review prostate biopsy slides before finalizing a treatment plan, especially when the case is borderline. This is a normal part of careful prostate cancer care, not a sign of a problem with the first read. If you are considering active surveillance, it is reasonable to ask whether your slides have been reviewed by a genitourinary pathology specialist.
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Common questions
Why is Gleason 3+4=7 not the same as 4+3=7?
The first number is the pattern that takes up the most space in your biopsy sample. The second is the next most common pattern. Both add up to 7, but in 4+3 the more abnormal pattern 4 dominates, and that is the more aggressive cancer. This is why your report lists both numbers rather than only the sum, and why 3+4 falls into Grade Group 2 while 4+3 falls into Grade Group 3.
Does my Gleason score tell me whether the cancer has spread?
No. Grade describes how the cells look under a microscope in the tissue that was sampled. Stage describes the size of the tumor and whether it has spread beyond the prostate. A biopsy only samples part of the gland, so the true highest-grade area can occasionally be missed. A Grade Group 4 cancer still inside the prostate is a different situation from the same grade found with spread to lymph nodes or bone.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-08-11 what this meansLast updated: 2026-08-16Next planned review: 2027-07-23
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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